Protein concentrates have long been recognized as an important component of processed foods. The need for protein is becoming more important as a basic nutritional requirement. New sources of protein concentrates are being sought to supplement the usual protein materials such as dry milk solids and soybean extracts. These protein concentrates are used in diet supplements and commercially prepared foods.
Protein concentrates have been much in demand particularly as fat substitutes. Natural fats have 9 Kcal (kilocalories) per gram, and proteins have 4 Kcal per gram, thus, replacing fats in foods with proteins results in a significant calorie savings. In addition, a diet high in fats has been linked with health disorders such as obesity, heart disease and atherosclerosis. Therefore, replacing the fats in foods with proteins has the desirable effect of improving the nutritional quality of the food, as well as reducing its caloric content. Protein concentrates can be used for this purpose; however, in order to be acceptable, the protein concentrates must be devoid of odors, flavors and colors which would render them unacceptable as a food substance.
Many proteins which are currently used in food processing are derived from vegetable sources, such as cereals and grains, or animal sources, such as milk solids. Many of these are described in the patent literature. In U.S. Pat. No. 4,376,133, J. R. Farand describes a process in which proteins derived from cereal grains, oilseeds or legume seeds are suspended in an organic solvent, then agglomerated by contacting the suspension with a polar solvent. This process forms solid agglomerates (up to 1000 microns in size) suitable for use in breakfast cereals and other foods, but which are not suitable as fat substitutes due to their agglomerated form and large size, or for microencapsulation purposes.
In U.S. Pat. Nos. 3,852,503 and 3,853,839, P. J. Magnino et al. describe a method for preparing an acid-stable soy protein product. The protein product is an aqueous slurry of soy protein which can be used directly as a component in processed foods (e.g., puddings), and can be dried to an acid-soluble powder.
In U.S. Pat. Nos. 3,891,777 and 3,891,778, R. A. Boyer describes a process for making cheese-like products from vegetable proteins. In this process, proteins derived from oil seeds (e.g., soybeans) are acid-precipitated to form a viscous curd, which is then processed to form a sliceable processed cheese product.
In U.S. Pat. No. 3,793,464, D. T. Rusch describes a process for preparing aqueous emulsions of proteins suitable for foods, in which the protein is coated with lipids in order to improve the taste and texture of the protein product, and to make it more palatable. The protein is first coated with the lipid layer, then dispersed in water.
In U.S. Pat. No. 4,734,287, N. S. Singer et al. describe a protein product based on dairy whey proteins which can be used as a fat substitute. The protein product produced by their method is composed of heat-labile particles of denatured dairy whey protein. In this process, whey proteins are heat-denatured under high shear conditions, and at low pH, to produce finely divided particles of denatured whey protein.
Proteins have also been used to encapsulate molecules. Encapsulation and microencapsulation have been widely applied in industry to protect the encapsulated mate, rial against light, oxygen, humidity, UV radiation and other hostile environments. Encapsulation can be employed to facilitate handling, to give protection against mechanical damage and to provide texture properties.
Microcapsules (i.e., microspheres) can range in size from tenths of a micron to several thousand microns, or larger. Currently available encapsulations use polymers as the encapsulant, such as polyacryldextrans (Edman et al., 1980, J. Pharm. Sci., 69: 838 and Artursson et al., 1984, J. Pharm. Sci., 73: 1507); or polyacrylamides (Ekman and Sjoholm, 1978, J. Pharm. Sci., 67: 693 and Ekman et al., 1976, Biochem., 15: 6115).
Microencapsulation is used in the food industry to improve the flavor, aroma, stability, appearance, nutritional value and texture of food products. With the increase in storage and transit time of processed food in industrialized countries, it is important to ensure nutritive value and sensory quality at least equal to the original food. In food applications, it is also important to have a safe, non-toxic, edible, biodegradable encapsulating material.